Thin-film circuit modules are commonly used in space-constrained applications, such as hearing instrument or cell phone products. In some thin-film circuit modules, perovskite or pyrochlore materials, such as (BaxSry)TiO3 (hereinafter BST), are used as high K capacitor dielectrics. The high dielectric constant of these materials allows for significant miniaturization of these devices. Many capacitors can also be fabricated on a single substrate along with other passive electronic components (integrated passive component chips) to form part of cellphone power amplifier modules, GPS receivers, etc.
Moisture affects pyrochlore and perovskite dielectric capacitors adversely, causing increased leakage and significantly degrading performance and shortening the lifetime of the device. Thus, either a hermetic package must be provided, or the chip must incorporate hermetic sealing layers to prevent moisture penetrating to the perovskite dielectric. For cost purposes, most applications incorporate a hermetic sealing layer.
Currently known methods for providing a hermetic seal and scratch protection include either a low-temperature plasma-enhanced chemical vapor deposition (PECVD) or high-temperature/low pressure deposition chemical vapor deposition process (LPCVD) of silicon nitride. These processes result in the production of a significant amount of atomic hydrogen.
Some of the hydrogen produced during the typical LPCVD and PECVD processes reacts with the perovskite or pyrochlore dielectric material and causes an increased leakage current in the capacitor. The lifetime of a capacitor is inversely related to leakage current. The LPCVD and PECVD processes, while useful for providing a hermetic seal and scratch protection, also cause a decrease in the lifetime of the capacitor, due to the effect of the hydrogen produced by these processes on the perovskite or pyrochlore materials.
Hydrogen barrier layers are known, but they have limited effectiveness. A typical hydrogen barrier serves to trap hydrogen ions and store them in the crystalline lattice without a change in the chemical composition of the barrier material. Atomized hydrogen easily diffuses through such barriers unless it reacts with them.